For the statistical analysis, Stata 8.0 will be used. The descriptive analysis will be composed of medians and proportions according to the nature of the variables, with its respective 95% confidence intervals. As a dispersion measurement the standard deviation will be calculated. The distribution of the variables will be studied using the Shapiro-Wilk test. To detect any difference between the groups, a T-test or a Wilcoxon test will be performed according to its distribution. The categorical variables will be compared using the Chi2 test or the exact Fisher's test. If required, a model of multiple logistic regressions or a covariance analysis will be done.